Re: Estimating project man hours (was: AS/400 Gasping For Air ??)

Dennis,

We use the following formula for estimating project time:
for each program: (number of files + difficulty) * experience

After years of spending time tracking we found that for an application if we
used:
(number of files + 4) * 4 we were pretty close to the overall time, but may be
very off on a particular program

BTW an update file counts as 2.  The lower the experience the higher the number.
We then take the hours and divide by 6 for man days.  We allow two hours per day
for administrative overhead not directly attributed to the project at hand.

We use a code generator and the time is split 25% design/documentation, 50%
programming/testing and 25% installation/training and post installation gotchas.

We do the design through a home grown tool which would help to make sure certain
things did not fall through the crack and along with generating code it would be
the basis for the documentation.  We determined that this tool reduced our
efforts by 20% over grunt coding or cut/paste. And reduced the possibility of
discrepancies between the actual system and the documentation.

Now that was for scratch development, for modifications we use (number of
programs affected * 2) * impact
Where impact may be minor (expand date field in file) to major (introduce
multiple language support)

This requires a veteran to determine the impact factor and we allow a 20% "we
forgot something" fudge factor.

None of this is an exact science, I guess that's why it's called an estimate.

James W. Kilgore
email@James-W-Kilgore.com

Dennis Lovelady wrote:

> <<snip>>

> Of course, a very large portion of that (or any) project would be in design,
> information gathering, "how to," user discussions, organization, file
> layouts, database design, process structure, goal definition, documentation,
> redesign, etc.  Probably, this is on the order of more than 50% of the
> project.  (Out of curiosity, what's a reasonable % for this sort of
> overhead?)  Given that the original question had to do with replacing an
> existing system, I still have to wonder if the estimate was not tremendously
> overstated, since most of that work has already been done (assuming that the
> new product will be an exact or near emulation of the original).  Still, the
> budgeted amount of the time would seem to be much too small for the project
> at hand.

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